Book Image

HashiCorp Packer in Production

By : John Boero
Book Image

HashiCorp Packer in Production

By: John Boero

Overview of this book

Creating machine images can be time-consuming and error-prone when done manually. HashiCorp Packer enables you to automate this process by defining the configuration in a simple, declarative syntax. This configuration is then used to create machine images for multiple environments and cloud providers. The book begins by showing you how to create your first manifest while helping you understand the available components. You’ll then configure the most common built-in builder options for Packer and use runtime provisioners to reconfigure a source image for desired tasks. You’ll also learn how to control logging for troubleshooting errors in complex builds and explore monitoring options for multiple logs at once. As you advance, you’ll build on your initial manifest for a local application that’ll easily migrate to another builder or cloud. The chapters also help you get to grips with basic container image options in different formats while scaling large builds in production. Finally, you’ll develop a life cycle and retention policy for images, automate packer builds, and protect your production environment from nefarious plugins. By the end of this book, you’ll be equipped to smoothen collaboration and reduce the risk of errors by creating machine images consistently and automatically based on your defined configuration.
Table of Contents (18 chapters)
1
Part 1: Packer’s Beginnings
7
Part 2: Managing Large Environments
11
Part 3: Advanced Customized Packer

Packer architecture

Packer itself is a fairly simple binary written in Go. It supports plugins for various inputs and outputs. The plugins that translate your configuration and scripts into artifact outputs are called builders. Common builders include common hypervisors such as VMware, QEMU, VirtualBox, AWS, GCP, and Microsoft Azure. Builders also include multiple container image formats, including LXC, LXD, Docker, and Podman. Many plugins have been contributed by the community and we will cover how you can write your own in a future chapter.

The bit of code you write to tell Packer what to do is called a template. Early versions of Packer expected your template to be written in JavaScript Object Notation (JSON). As of Packer version 1.7.0, both JSON and HashiCorp Configuration Language version 2 (HCL2) are supported, with the latter being preferred. We will cover both formats and how you can migrate a JSON template into an HCL2 template shortly.

Provisioners are tasks or resources that should be applied to your image before packaging. By default, each builder in your template takes each provisioner. Take an example where you want to build a system image with your application across AWS, Azure, and GCP. All you need to do is define your list of builders for AWS, Azure, and GCP and include a single provisioner that uploads your application.

A build job is what runs the Packer build command with your template. Normally, this forks a parallel process for every builder you specify in your template. A build can happen simultaneously across VMware, AWS, Azure, GCP, or other builders while Packer tracks the results and reports any errors. When all builders finish or end in an error, the job is done and the Packer process terminates. Optionally, Packer may compress output images before terminating, to save space.